The invention concerns an inflatable, helical cuff which is implantable and functions as an occluder, sensor, or transducer when intimately engaged with a tubular body member (e.g., nerve cord, esophagus, colon, intestine or blood vessel).
The accurate measurement of blood pressure is necessary, in the treatment of volatile hypertension, the diagnosis of arteriosclerosis, and in the prevention of strokes, for example. The least complicated blood pressure measuring device is the common non-invasive cuff which is fastened about a patient's arm and inflated. However, very accurate blood pressure measurement is not possible since atmospheric pressure directly influences the cuff's operation. Jackson discloses in U.S. Pat. No. 4,160,448 a cannula for determining blood pressure, which is inserted into the blood stream through a needle, to locate a flaccid, relaxed wall directly in the blood stream. The relaxed wall allows direct transmission of the blood pressure to a neutral liquid in the cannula. The pressure of the cannula's liquid is transmitted out of the blood vessel to a remote pressure responsive indicator. Use of such an invasive device obviously increases the risk of damage to and infection of the blood vessel. U.S. Pat. No. 4,190,057 to Hill et al concerns a device for determining the patency of a blood vessel. A bulb of flexible material is arranged in pressure transferring relationship with a wall of a vein. A cuff is tied around the bulb and the vein to hold them in a confined relationship. Connected by a catheter to the bulb is a thick walled reservoir which is implanted just under the patient's skin. The wall of the reservoir is punctured by a hypodermic needle which is connected to a pressure indicator.
Accurate blood flow measuring devices are generally calibrated to a blood vessel having zero velocity blood flow. To accomplish zero velocity in a blood vessel, occluders of an appropriate diameter, such as produced in various sizes by In Vivo Metric Systems, are used to close off the blood vessel. Such occluders consist of an inwardly inflatable C-ring which is tied about a blood vessel and inflated until the blood vessel is fully constricted. Because blood flow through the occluded area is impossible, a zero velocity measurement is obtainable. Other members of the body, such as the esophagus, colon, intestine, and nerve cords are occluded during surgery or for research purposes. However, these members are most often sewn, clipped or tied to prevent flow through the member.
Helical structures have been used in esophageal and cardiovascular grafts, as taught by U.S. Pat. Nos. 3,479,670 to Medell and 4,300,244 to Bokros, respectively. The esophageal graft includes a cylindrical tube which is wrapped with two sections of monofilament to form a right-hand helix and a left-hand helix along the surface of the tube. The resultant structure is heated, causing the monofilaments to fuse as a support for the tube. The cardiovascular graft uses a spring to join segments of a severed blood vessel. The spring may be joined at each end to the blood vessel segments by suturing or may be fitted to a rigid fitting which is secured about the blood vessel segments.